[vsnet-grb-info 7951] GRB 090607: Swift-BAT refined analysis of the SHB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9494
SUBJECT: GRB 090607: Swift-BAT refined analysis of the SHB
DATE:    09/06/07 11:32:02 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC) D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090607 (trigger #354299)
(Marshall, et al., GCN Circ. 9491).  The BAT ground-calculated position is
RA, Dec = 191.194, 44.108 deg, which is 
   RA(J2000)  =  12h 44m 46.7s 
   Dec(J2000) = +44d 06' 28.4" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.
 
The mask-weighted light curve shows two narrow peaks.  The first starts
at T-0.1 sec, peaks at T+0.1 sec, and ends at T+0.7sec.  The second peak
starts at ~T+1.7 sec, peaks at T+2.2 sec, and ends at T+2.5 sec.  There is
no hint of emission out to at least T+243 sec.  T90 (15-350 keV) is
2.3 +- 0.1 sec (estimated error including systematics).
 
The time-averaged spectrum from T+0.1 to T+2.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.25 +- 0.30.  The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.01 sec in the 15-150 keV band
is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

Based on the shortness of the duration and the spectral hardness, we believe
this to be a short hard burst.
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/354299/BA/